not much , quite possible we could get some action going in the western Caribbean, typically these monsoonal systems are very broad and its tough to squeeze much cyclone development early in the season...not the conditions are somewhat fair for development( barring a meandering TUTT in the region) might wanna keep an eye out...OP GFS has been hinting at this for a week or so, it has weak ensemble support attm...

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Global Tropical Hazards Assessment Discussion

Last Updated: 09.13.11 Valid: 09.14.11 - 09.27.11

The MJO index amplitude was weak during the past seven days and other modes of tropical subseasonal variability remain generally weak. During the past week, enhanced rainfall was observed across the western equatorial Indian Ocean, northern India, parts of southeast Asia, and the eastern Maritime Continent. Enhanced rainfall was also observed in the Gulf of Campeche and south-central Mexico, associated with Tropical Storm Nate. Suppressed rainfall was observed over the eastern equatorial Indian Ocean. Tropical Storm Maria formed in the eastern Atlantic and brought precipitation to the eastern Caribbean Sea. In the northwest Pacific, Tropical Storm Kulap developed and moved into the Yellow Sea. Tropical Depression 18 also formed in this region and is moving toward the Yellow Sea.

There is a lot of spread amongst the dynamical model MJO index forecasts during the upcoming 1-2 week period. A few models indicate some eastward propagation of a weak signal during Week-2. Based on recent observations and the high degree of uncertainty with the MJO index model forecasts, the MJO is forecast to remain weak during the period. The MJO is not expected to contribute substantially to anomalous tropical convection across the global tropics during the period at this time.

During Week-1, an enhanced monsoon flow is expected to enhance rainfall in northern India, the Bay of Bengal, and Southeast Asia. Above average sea surface temperatures are likely to enhance rainfall in the western equatorial Indian Ocean. Lower tropospheric convergence over central Africa is expected to enhance rainfall in the region, while a ridge of high pressure and anomalous northerly flow is expected to suppress convection in north-central Mexico.

A high chance of tropical cyclone development exists in the northwest Pacific as tropical depression 18W is forecast to intensify to a tropical storm. Behind this system is another disturbance that has a moderate chance of developing into a tropical cyclone since upper level conditions are favorable for development at this time. A broad area of low pressure in the western Caribbean Sea is expected to bring widespread precipitation to the region and Central America. A tropical wave in the eastern Atlantic increases the threat for tropical cyclone development in the region.

During week-2, signals are rather weak for anomalous convection across the global tropics. However, monsoon flow is expected to remain enhanced across the Bay of Bengal and parts of Southeast Asia. Model guidance and above average sea surface temperatures also favor enhanced convection in the western Indian Ocean. Moderate chances for tropical cyclone development are expected in the main development region of the eastern tropical Atlantic as robust easterly waves continue to exit Africa. There is a moderate chance of tropical cyclone development in the western Caribbean Sea associated with a broad area of low pressure, forecast low wind shear, and warm sea surface temperatures.

Global Tropical Hazards Outlook DiscussionLast Updated: 09.27.11 Valid: 09.28.11 - 10.11.11The MJO strengthened during the past week and this appears to be the primary mode of subseasonal coherent tropical variability ongoing. Atmospheric Kelvin wave and equatorial Rossby wave activity are playing lesser roles at the current time. The enhanced convective phase of the MJO is currently centered over the eastern Maritime continent. The Asian monsoon circulation remained enhanced over the first portion of the past week, but has weakened in recent days.

Enhanced convection was observed from the Bay of Bengal to the western Pacific with drier-than-average conditions already developing across India and parts of the Indian Ocean. The WH MJO index showed an increase in amplitude and irregular eastward propagation over the past week and this behavior, in general terms, was well forecast by most operational model forecasts one week ago. It was an active period for tropical cyclone activity as storms developed in the western and eastern Pacifc and the eastern Atlantic basins.

The MJO is forecast to remain active for the next two weeks and its enhanced phase is forecast to shift from the far eastern Maritime continent across the western Pacific. The amplitude of the MJO index forecasts indicates at least moderate strength activity for the next two weeks.

For Week-1, enhanced rainfall is forecast from southeast China and across the western Pacific Ocean while suppressed rainfall is favored from India to the western Maritime continent primarily associated with the MJO. Typhoon Nesat and its remnants also will contribute to enhanced rainfall later in the period for parts of Southeast Asia and southeast China. Tropical cyclone activity remains favored across the western Pacific east of the Philippines associated with the MJO and this activity is farther south than that seen earlier in the season. Hurricane Hillary in the eastern Pacific is moving northward toward the U.S., but is forecast to weaken. There is potential for remnant moisture from Hillary to increase the threat for above average rainfall and potential localized flash flooding across the southwest U.S. and southern Rockies. There is high model spread with this event so confidence is generally low.

During Week-2, with eastward propagation of the MJO signal, the large scale areas of enhanced and suppressed convection shift eastward over the eastern Hemisphere. Tropical cyclone activity remains favored over the western Pacific. The MJO may begin to increase the chances for tropical cyclone activity across the eastern Pacific late during Week-2 as well as elevate chances for above-average rainfall over parts of southern Central America and northwest South America.

For the U.S., the forecast MJO phase during this time of the year favors above-normal temperatures across portions of the central U.S. and adds support to current model forecasts in this area during the next 1-2 weeks. The current MJO activity is expected to contribute considerable energy and moisture to a strong Pacific Jet and favors much above-average precipitation across the Pacific Northwest during late Week-1 and Week-2.

The MJO remained active during the past week with the enhanced convective phase shifting from the Maritime continent to the western Pacific and its focus is primarily north of the equator. Atmospheric Kelvin wave (KW) activity continues to be superimposed on the slower ongoing MJO variability and an equatorial Rossby wave (ERW) has contributed to maintaining enhanced convection across Southeast Asia. The Asian monsoon circulation was much weaker than in previous weeks. Enhanced convection was observed from Southeast Asia across the western Pacific and also across much of west-central Africa. Drier-than-average conditions were observed over India, the western Maritime continent and various areas across the tropical western hemisphere. Super typhoon Nalgae impacted the Philippines with dangerous winds and heavy rainfall during the past week.

The WH MJO index showed continued eastward propagation during the past week, but this movement has slowed in recent days most likely because it is being impacted by westward moving convective activity in the far western Pacific and Southeast Asia. The observed evolution of the MJO index was somewhat well forecast from both one and two weeks ago,although the amplitude of the index as forecast by the models was too weak and in some instances too fast.

The MJO is forecast to remain active with MJO index model forecasts indicating continued eastward propagation of the enhanced convective phase from the western Pacific to the western hemisphere (WH phase 6 to 8) over the next two weeks. There is very good model agreement in this forecast. At the current time, the amplitude of the MJO index forecasts favors at least moderate strength MJO activity.

For Week-1, enhanced convection is forecast from the South China Sea into the western Pacific and suppressed convection is favored from India across the eastern Indian Ocean to Indonesia primarily associated with the MJO. tropical cyclone Nalgae is expected to result in heavy rainfall very early in the period across parts of southeast Asia. Tropical cyclone development remains a threat east of the Philippines as the enhanced phase of the MJO exits this region. The MJO favors tropical development in the eastern Pacific and enhanced rainfall across portions of Central America and northern South America during this period.A frontal boundary and general low pressure favors enhanced rainfall for the Bahamas and parts of the Caribbean islands and Florida and increases the threat for tropical devlopment north of Cuba in close proximity to Florida during Week-1. Model forecast guidance continues to favor above-average rainfall for areas in west central Africa.

The area of suppressed convection in the eastern hemisphere is forecast to shift eastward and encompass the Maritime continent and begin to impact the western Pacific. Later during Week-2, there is some potential for convection to increase across east central Africa and the western Indian Ocean ahead of the next enhanced convective phase of the MJO. During Week-2, the MJO signal continues the threat for tropical cyclone development in the eastern Pacific and enhanced rainfall in the Americas as well as increases the chances of tropical cyclone development in the western Caribbean Sea.

For local U.S. interests, the forecast MJO phase would favor continued potential for above-average precipitation for the Northwest quarter of the U.S. during much of the period including parts of California. The MJO also increases the threat for tropical cyclogenesis in the western Caribbean Sea during Week-2 and if development occurs the Southeast U.S. should monitor for a potential track to the north and east.

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICALSTORM PHILIPPE...LOCATED ABOUT 1215 MILES WEST OF THE AZORES.

1. A SURFACE TROUGH LOCATED FROM THE EXTREME NORTHWESTERN CARIBBEAN SEAACROSS CENTRAL CUBA AND INTO THE CENTRAL BAHAMAS IS PRODUCINGWIDESPREAD CLOUDINESS AND THUNDERSTORMS OVER MUCH OF CENTRAL ANDEASTERN CUBA...MOST OF THE FLORIDA PENINSULA AND THE FLORIDAKEYS...ALL OF THE BAHAMAS...AND ADJACENT ATLANTIC WATERS. THE TROUGH HAS BECOME A LITTLE BETTER DEFINED AND SURFACE PRESSURES ARESLOWLY FALLING. GRADUAL DEVELOPMENT OF THIS LARGE AREA OF DISTURBEDWEATHER IS POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES WESTWARD ORNORTHWESTWARD AT 5 TO 10 MPH. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL OR SUBTROPICAL CYCLONE DURINGTHE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...THIS DISTURBANCEWILL PRODUCE STRONG GUSTY WINDS AND LOCALLY HEAVY RAINFALL ACROSSPORTIONS OF THE BAHAMAS AND THE FLORIDA PENINSULA OVER THE NEXTCOUPLE OF DAYS. ADDITIONAL INFORMATION ON THIS DEVELOPING GALE AREACAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHERSERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THENEXT 48 HOURS.

The 12z and 18z GFS both show something developing in the Caribbean (12z was a western development and 18z was a central development) and moving over Cuba into the Bahamas and off the east coast in the 240 through 384 hour range.